Highly stereocontrolled synthesis of substituted propiolactones and butyrolactones from achiral lithium enolates and homociral aldehydes
作者:Iosune Arrastia、Begon̄a Lecea、Fernando P. Cossío
DOI:10.1016/0040-4039(95)02139-6
日期:1996.1
Lithiumenolates derived from achiral thiol esters react in a highly stereoselective fashion with homochiral aldehydes to yield the corresponding 2-oxetanones. The stereochemical outcome of the reaction corresponds to a non-chelation control. except when O-silylated mandelaldehyde is used. The propiolactones thus formed are efficiently transformed into δ-lactones via Lewis acid promoted dyotropic rearrangements
Origins of Stereocontrol in the [2 + 2] Cycloaddition between Achiral Ketenes and Chiral α-Alkoxy Aldehydes. A Pericyclic Alternative to the Aldol Reaction
作者:Begoña Lecea、Ana Arrieta、Iosune Arrastia、Fernando P. Cossío
DOI:10.1021/jo9806512
日期:1998.7.1
Ab Initio calculations predict that the thermal [2 + 2] cycloaddition reaction between C(2 upsilon)-symmetric ketenes and enantiopure aldehydes takes place with high enough stereocontrol for preparative purposes. The sense of induction is predicted to be non-Felkin. It is also found that the [2 + 2] cycloaddition involving nonactivated ketenes is facilitated by using 5 M solutions of lithium perchlorate in diethyl ether. It is found that both the purely thermal and lithium-assisted [2 + 2] cycloadditions result in the same type of stereocontrol. This method constitutes a general route for the synthesis of homochiral 2-oxetanones and related compounds, thus providing a pericyclic alternative to the aldol reaction.